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thinking of programming a naff version of space invaders ...
http://www.retrosoftware.co.uk/forum/viewtopic.php?f=42&t=222		 Page 4 of 6
Author:  NeilB [ Fri Feb 13, 2009 3:03 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
I know!!! I know!!

I'm assuming it's because I've starting at 0x0d00 - but as I've said - there is a little bloat ware included.
I blame my inexperience! I haven't had time to play around with loading stuff in from disk - so it's all incbin'd.

Well, the BETA is done. So, I can get the code in a state for review. Hopefully there will only be minor issues found, then I'll release the source. I'll have to steel-up my spine - in prep for the onslaught of feedback when that happens! :lol:

I noted the site was down for a while - so hopefully the wiki is updated with the latest sparse invaders ...

I'll await the feedback on this version - and update the wiki over the weekend... Hmm it's been a long week and I did a BIG VODKA!!

Oh, small question - can someone explain exactually what the difference is with the two instructions below...?

STA (userptr,X)

STA (userptr),Y

I fully understand the second, not sure about the above one (indirect with X) hmmm! :shock:

Thanks all, Neil
Author:  DaveF [ Fri Feb 13, 2009 3:12 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
NeilB wrote:
I know!!! I know!!

Hehe, just teasing. I'm struggling with memory myself :(

Quote:
Well, the BETA is done. So, I can get the code in a state for review. Hopefully there will only be minor issues found, then I'll release the source.

Excellent, I'll have a play in an hour or so. Get me in the mood for the weekend!

Quote:
Oh, small question - can someone explain exactually what the difference is with the two instructions below...?


I use this quite a lot: http://www.obelisk.demon.co.uk/6502/index.html
Author:  DaveF [ Fri Feb 13, 2009 3:23 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
Couldn't wait an hour :-)

When you complete the wave with the "mothership" going across the top, it continues to go across the top on the next wave. Is that intentional?

Other than that, looking grand! Pour yourself a vodka!
Author:  RichTW [ Fri Feb 13, 2009 4:56 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
LDA (ind,X) is a weird one.

The best way to explain it is with an example.

Suppose we have LDA ($20,X) with X = $30.

* First it calculates addr = $20 + X = $50
* Then it uses $50 and $51 as the LSB/MSB of the address to access

If $50 contains $AA, and $51 contains $BB, the final result is

A = contents of address $BBAA.

Phew!

It sounds contrived, but I remember finding it moderately useful in my background music player - e.g. suppose you want to play a tune on three sound channels, and you have a data pointer for each sound channel. Then you can write something like:

Code:
channel1ptr = $70
channel2ptr = $72
channel3ptr = $74
channel1counter = $76
channel1envelope = $77
channel2counter = $78
channel2envelope = $79
channel3counter = $7A
channel3envelope = $7B

    LDX #4
.loop
    DEC channel1counter, X
    BNE skipthischannel
    LDA (channel1ptr, X)
    INC channel1ptr,X
    BNE nocarry
    INC channel1ptr+1,X
.nocarry
    LDY channel1envelope,X
    JSR playdata
.skipthischannel
    DEX
    DEX
    BPL loop
Author:  NeilB [ Fri Feb 13, 2009 5:32 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
Thanks Rich!

I need to study it more - but it makes sense by the results I was getting! ;-)

Oh, thanks Dave also for having a play ... As for the mother ship - yeap - I left it as is - just because it might allow another attempt at the start of another level ... Call it artistic licence! :lol:
I'm glad you enjoyed it


Looking forward to more feedback!
[Robotic voice] "Need Feedback! Need Feeback!"
The above was nominated for 'terrible joke of the week!'

thanks - Neil
Author:  NeilB [ Fri Feb 13, 2009 5:37 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
RichTW wrote:
LDA (ind,X) is a weird one.

The best way to explain it is with an example.

Suppose we have LDA ($20,X) with X = $30.

* First it calculates addr = $20 + X = $50
* Then it uses $50 and $51 as the LSB/MSB of the address to access

If $50 contains $AA, and $51 contains $BB, the final result is

A = contents of address $BBAA.

Phew!


Dooh - It's clicked!! No wonder it wasn't doing the same as (ind),Y - I feel slightly silly! LOL

Thanks again Rich!
Author:  DaveM [ Fri Feb 13, 2009 9:46 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
Downloaded.

Played it.

Liked it.

Have a few ideas/comments and will leave some feedback soon! :)

P.S. Still no sign of an N Beresford on the Byte Back attendee list ... tickets are flying out at the moment (190 sold, just 60 left) so I wouldn't hang around too much longer! ;)
Author:  NeilB [ Fri Feb 13, 2009 10:25 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
DaveM wrote:
Downloaded.

Played it.

Liked it.

Have a few ideas/comments and will leave some feedback soon! :)

P.S. Still no sign of an N Beresford on the Byte Back attendee list ... tickets are flying out at the moment (190 sold, just 60 left) so I wouldn't hang around too much longer! ;)



OK, got a ticket for Saturday!! Meet you up there!! I like smooth if you're going to the bar!!! ;-)
Author:  DaveF [ Sat Feb 14, 2009 8:39 am ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
NeilB wrote:
OK, got a ticket for Saturday!! Meet you up there!! I like smooth if you're going to the bar!!! ;-)

Good man, that's the spirit! Looks like there's going to be loads of us at this one!
Author:  DaveM [ Mon Feb 16, 2009 4:27 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
NeilB wrote:
OK, got a ticket for Saturday!! Meet you up there!

Wahey! :)

Ok, I'm just gonna update my record of who's bringing what to Byte Back (in terms of kit) then I'll be having a proper bash on Sparse!
Author:  NeilB [ Tue Feb 17, 2009 2:15 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
I've just update the WIP page for Sparse Invaders.

Hopefully I'll get a little feedback and maybe get a release out for you guys, if you fancied showing it at the Show in March ... Hahaha or am I being a cheeky so and so. :lol:

Anyway, just wanted to inform you that the WIP is updated.

Back to work for me, Neil
Author:  Samwise [ Tue Feb 17, 2009 2:49 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
Neil,

Wrt your question on the wiki about acquiring a suitable license, you might want to take a look through this topic, where various licenses have been discussed.

Sam.
Author:  NeilB [ Tue Feb 17, 2009 3:06 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
Thanks Sam!
I've had a quick look - and it's what I need, cheers!
With using said license, I imagine I would supply the full license agreement in a text file with the source, and a header for each of the source files.

Err, if anyone has a GPL version 3 header I could use with the source - it will buy my friendship for at least a week! :lol:

- Neil
Author:  Samwise [ Tue Feb 17, 2009 3:19 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
err ... not sure I'm following. It sounds like you're intending to use GPL v3? (in which case, I assume you know that your software /could/ then be used to create a derivative that could be sold commercially, but that that derivative would have to have it's source code released as GPL too).

In which case, here's a pretty easy guide to how to license your code:

http://www.gnu.org/licenses/gpl-howto.html

We already went through this process with Farmyard Fun, which is also released under the GPL v3 license (the program is in BASIC, so source code is available).

Sam.
Author:  NeilB [ Tue Feb 17, 2009 3:35 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
Oh confusion... This is the problem when trying to read over stuff while pretending to work! LOL

I just want a license that allows people to use and abuse freely but not for commercial use.

I will read up later, thanks for pointing out the error or my ways Sam,

Neil
Author:  Samwise [ Tue Feb 17, 2009 5:21 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
As suggested in the other topic, the only major one I found which might be free for non-commercial use was:

Creative Commons Attribution-Non-Commercial 3.0 Unported Licence (BY-NC)
http://en.wikipedia.org/wiki/Creative_Commons_licenses

So you could use that but, tbh, I think it's highly unlikely that anyone would try to sell on Sparse Invaders. To that end, if it were me, I'd probably just GPL the code, as that seems to be the closest to your intent and it's much more battle tested than the Creative Commons licenses. Even if someone did try to sell on your GPL code or a derivative, they have to provide the source code for it to anyone who's purchased the game so the game's source would still be out there, maybe even improved - and we can take that source back and host it ourselves, if we wanted. Realistically, though, if they were going to spend much time improving on it, they'd probably end up re-writing it completely, I assume, in order to fit it into the beeb ...

Sam.
Author:  NeilB [ Tue Feb 17, 2009 6:30 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
Thanks Sam,

well, GPL it is.

And the changes of anyone selling it are very slim, borderline FLAT... 8-)

Just nice to be covered.

As for fitting it on the beeb, that shouldn't be a problem, I've just been lazy, and really wanted to get the game out there and play-tested.

I'm looking forward to getting the code together for a group review ( for placing on the site for general consumption, not optimizing or ... well you know! :D )

Neil
Author:  DaveM [ Tue Feb 17, 2009 6:36 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
NeilB wrote:
And the changes of anyone selling it are very slim, borderline FLAT... 8-)

Ahem! ;)

Actually, as per my recent post in the Release Formats thread, I would like to be able to offer packaged versions of free downloads should anybody want one (e.g. £0.95p for a tape or £1.50 for a disc).

Would the license still be valid if we did this?
Author:  NeilB [ Wed Feb 18, 2009 12:07 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
Sure Dave, :lol:

you can sell all the copies you want! I'll be buying one! :D

I am just thinking of bedroom-joe who decides to sell it, or a slightly modified version.

As far as RetroSoftware is concerned, you sell all you want!!

thanks Dave,

Neil
Author:  NeilB [ Thu Feb 19, 2009 8:48 pm ]
Post subject:  Re: thinking of programming a naff version of space invaders ...
OK ... New alert!

Working late, so have fixed the BBC B memory issue. Just really had to remove debug functionality, rewrite the hiscore, rework block draw and remove unwanted code. Saved several hundred bytes doing that! So, I've about 71 bytes left before it runs into vide memory!

:o

:lol:

Well, would be good to get it tried...

thanks - Neil
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